Bump toolkit & apply fixes

The latest toolkit changes the media mixin so
the styles in media-queries don't get dumped into
the main block for IE<9.

Overwrites for the above condition are therefore
no longer needed.
Remove testing reference again
Merge pull request #245 from alphagov/correct-campaign-css

Bump toolkit & apply fixes
Changes to guides nav
Switch to correct https rubygems source

 is deprecated
Merging